1. Field of the Invention
The present invention relates to cholesterol-lowering agents. More particularly, it is concerned with cholesterol-lowering agents containing an anion-exchange resin as an active component.
2. Description of Prior Art
Relationship between serum lipid and atherosclerotic diseases has been discussed for a long time. Recently, it has been elucidated scientifically that reduction of the serum cholesterol level can prevent the onset of coronary heart disease or the death from such disease [Journal of the American Medical Association (JAMA), vol. 251, pp. 351-364 (1984)].
It is also known that certain anion-exchange resins possess a serum cholesterol-lowering activity. Mechanism of the action is believed to lie in binding the anion-exchange resin with bile acids in the intestinal tract which in turn inhibits resorption of the bile acids and consequently promotes conversion of cholesterol existing in the liver in equilibrium with bile acids to bile acids thereby reducing serum cholesterol. Heretofore-known anion-exchange resins developed for removing bile acids in the intestinal tract by such binding are those disclosed in British Patent No. 929391, Japanese Patent Publication No. 54457/1986, Japanese Patent Laid-open to Public Nos. 150017/1981 and 142920/1982, etc. Typical of them is, for example, cholestiramine which is an amino resin (British Patent No. 929,391).
Whereas these resins have a large ion-exchanging capacity, they are not necessarily capable of selectively binding bile acids when acid substances are present in addition to bile acids in the intestinal tract. As a matter of fact, there are co-existing in the intestinal tract acid substances such as acidic proteins, amino acids and organic acids which bind with anion-exchange resin as a pair ion. Under such conditions, the amount of binding with bile acids is not necessarily large. It is therefore required that composition of the resin is designed so as to bind bile acids more selectively than binding other co-existing acid substances. Cholestiramine cannot necessarily be said to be satisfactory in percent inhibition of increase of serum total cholesterol.
It is an object of the invention to provide cholesterol-lowering agents more selectively binding bile acids thereby being more highly inhibitory against increase in serum total cholesterol.